Phylogenetic analysis of macrorestriction fragments as a measure of genetic relatedness in Staphylococcus aureus: the epidemiological impact of methicillin resistance

The present study was undertaken for the purpose of defining the epidemiology and genetic relatedness of Staphylococcus aureus strains in a region of Italy by investigating the molecular background for which resistance to methicillin, mediated by the acquisition of another penicillin-binding protein gene, is embedded. Restriction fragment length polymorphism (RFLP) data were used for phylogenetic analyses, since genetic distance values can be used as a general measure of the number of events generating distinct clones. The percentages of methicillin-resistant S. aureus (MRSA) isolates in a six-month period from inpatients and outpatients were, respectively, 12% (22 out of 180) and 0.4% (1 out of 257). On the basis of RFLP obtained after pulsed field gel electrophoresis (PFGE), it was possible to designate isolates as indistinguishable, closely related, possibly related and unrelated. We were able to demonstrate the occurrence of at least five distinct MRSA cross-infection episodes in two hospitals, four involving two patients each and one involving four patients. Phylogenetic analyses overcame the simple pairwise comparison of common bands between strains, and provided a comprehensive epidemiological scenario, identifying three major clusters of MRSA, including different levels of genetic relatedness, while excluding the circulation of a single clone in Italy. Moreover, multidimensional scaling analysis of the obtained genetic distance confirmed that MRSA strains belong to a restricted set of clones, thus demonstrating the relatedness of broad evolutionary lineages within the species S. aureus.

[Replacement of the aortic valve with a pulmonary autograft: experience at the University of Verona]

BACKGROUND

Early and long term results after surgical replacement of the aortic valve depend to a large degree on the type of valve substitute used. Pulmonary autograft offers many theoretical advantages, particularly in young patients.

METHODS

Between July 1994 and August 1996, 15 patients (12 male) with a mean age of 28 +/- 6 years (range 14 to 36 years) were selected for aortic valve replacement with a pulmonary autograft. The aortic valve disease was isolated insufficiency in 7 cases (47%), stenosis in 3 (20%) and mixed lesion in 5 (33%). One patient in the last group had bacterial endocarditis (Streptococcus mitis). Seven patients (47%) had a bicuspid aortic valve. In 3 cases (20%) the autograft was inserted as a scalloped subcoronary implant. Twelve patients (80%) had total aortic root replacement with re-implantation of the coronary ostia. The right ventricular outflow tract was reconstructed with a cryopreserved homograft (13 pulmonary; 2 aortic). The aortic cross-clamp time was 156 +/- 18 minutes with a total bypass time of 221 +/- 26 minutes.

RESULTS

All patients survived the operation. Three postoperative bleeding (20%) necessitated re-exploration. Mean post-operative hospital stay was 10 +/- 2 days. All patients were discharged on aspirin for the period of three months. One patient (7%) with moderate neo-aortic valve insufficiency died suddenly 11 months post-operatively. All survivors are asymptomatic, in NYHA FC 1 at a mean follow-up time of 15.7 months. Freedom from reoperation, valve related complication and endocarditis is 100%. Two-dimensional (2-D) echocardiography six months postoperatively showed a mean left ventricular outflow gradient of 13 +/- 4 mmHg with no evidence of aortic regurgitation in 11 cases (78.5%) and trivial in 3 (21.5%).

CONCLUSIONS

Although the Ross operation is technically more challenging and requires a longer operating time than standard procedures, this does not seem to affect early mortality and morbidity. Clinical and haemodynamic results appear to be gratifying. Continued patients evaluation particularly with regard to evidence of valve degeneration and arrhythmias in the long term is warranted.

Molecular typing of Klebsiella pneumoniae isolates from a neonatal intensive care unit

The epidemiological features of 60 multiresistant K. pneumoniae strains isolated from 1991 to 1995 in a neonatal ward are described. Antibiotic. Susceptibility testing and plasmid profile analysis were used as subtyping procedures. Antibiotic susceptibility typing was not informative enough since discrimination among isolates was typically poor. Plasmid profile analysis demonstrated that 58 out of 60 strains harboured one or more plasmid DNA bands, of different molecular weights ranging between 1.8 and 150 Mda. Small plasmids were best visualized after the alkaline lysis procedure, while large plasmids by the Kado and Liu method. A combination of plasmid patterns obtained by the two extraction procedures was used to define the final plasmid profile for each strain. Thirteen different plasmid profiles were identified among the collection of K. pneumoniae isolates from newborn patients of the same intensive care unit. The investigation showed that the strains were not responsible for a single outbreak.

Evidence for tumor necrosis factor alpha as a mediator of the toxicity of a cyclooxygenase inhibitor in Gram-negative sepsis

To investigate the effect of cyclooxygenase inhibition in experimental Gram-negative sepsis, indomethacin was administered to mice at different times (1 or 5 days, or 1 h) before sublethal infection with an intravenous inoculum of Pseudomonas aeruginosa Early indomethacin exposure did not alter the outcome of infection, yet treatment at the time of bacterial challenge resulted in a high mortality rate. Polymerase chain reaction-assisted mRNA amplification in the spleens of infected mice revealed that tumor necrosis factor alpha (TNF-alpha) messenger was selectively expressed by the drug-treated and infected mice during the 24 h preceding death. Higher TNF-alpha levels were found in sera from these mice, whose macrophages produced increased levels of nitric oxide in vitro. Both pentoxifylline, an inhibitor of TNF-alpha synthesis, and an inhibitor of nitric oxide production improved survival in the indomethacin-treated and infected mice, although no such effect followed the administration of TNF-neutralizing antibodies. These data support the notion that cyclooxygenase inhibitors may exert both positive and negative effects in Gram-negative sepsis, the latter presumably involving overproduction of TNF-alpha.

Study of a melanic pigment of Proteus mirabilis

The present study sought to determine whether the pigment produced by Proteus mirabilis from the L-forms of various aromatic amino acids under aerobic conditions is melanic in nature. It is a black-brown pigment which behaves like a melanin in many respects, namely solubility features, bleaching by oxidizing agents and positive response to the Fontana-Masson assay. In the present study, for the first time, it was shown by electron spin resonance analysis that a bacterial melanin is able to act as a free radical trap, as was previously demonstrated for other melanins. Scanning electron microscopy studies showed a specific organized structure of the pigment as rounded aggregates of spherical bodies. DNA hybridization data did not reveal, in the P. mirabilis genome, any nucleotide sequence related to Shewanella colwelliana mel A, one of the two melanogenesis systems already defined at the molecular level in bacteria. Results obtained from experiments on pigment production inhibition suggest a possible role of tyrosinase in P. mirabilis melanogenesis. In conclusion, from the bulk of our results, it appears that the pigment produced by P. mirabilis is melanic in nature.

Preliminary experience with pulmonary autografts

Between July 1994 and March 1995, seven patients (six male) with a mean age of 27 years (range 18 to 34 years) were selected for aortic valve replacement with a pulmonary autograft (Ross operation). The aortic valve disease was isolated insufficiency in four cases, stenosis in one and mixed lesion in two. Three patients had a bicuspid aortic valve. Previous cardiac surgical procedures had been performed in two cases (coarctation repair and valvuloplasty in one; isolated aortic valvuloplasty in one). Two patients were in NYHA class II and five in class III. In two cases the autograft was inserted as a scalloped subcoronary implant. Four patients had total aortic root replacement with re-implantation of the coronary ostia. The RVOT was reconstructed with a cryopreserved homograft (five pulmonary two aortic). The aortic cross-clamp time was 150 +/- 10 minutes with a total bypass time of 212 +/- 14 minutes. There was neither operative nor late mortality. Postoperative echocardiography revealed trivial autograft insufficiency in one case with a mean transvalvular gradient of 15.8 mmHg. All patients improved symptomatically (100% in NYHA class I). Freedom from reoperation, valve related complications and endocarditis is 100% at a mean follow up of 5.6 months (range 1-9 months). This preliminary experience supports the concept of pulmonary autograft implantation in selected patients.

Laparoscopy-guided drainage of hepatic abscess

Hepatic abscess is a serious surgical condition with a mortality rate of up to 63% reported if not adequately treated. Laparotomy and computed tomographic (CT) guidance have been used to drain these collections, each with their own problems. Herein we describe a method of draining laparoscopically a hepatic abscess. A 45-year-old Haitian man presented with night sweats and fevers to 103 degrees F; he was diagnosed by CT to have a large (7 cm) abscess in the posterosuperior portion of the right hepatic lobe. The CT-guided drainage yielded only 8 cc fluid. The patient underwent laparoscopy-guided drainage of the abscess with placement of intra-hepatic and perihepatic drains. The patient had dramatic clinical improvement with no morbidity from the procedure. A follow-up CT of the abdomen revealed near-complete disappearance of the abscess cavity within 48 h. A straightforward method of laparoscopic drainage of hepatic abscesses is presented in detail. It provides a simple alternative for drainage with excellent results and minimal morbidity.

Long-term results of mitral commissurotomy

Between January 1968 and December 1989, 280 patients underwent conservative surgical treatment for pure mitral stenosis. Closed commissurotomy was utilized in 134 patients, with a mean age of 38 +/- 11 years and a mean valve area of 1.0 +/- 0.29 cm2. Open commissurotomy was performed in 146 older patients (mean age 44 +/- 11 years) with a mean valve area of 0.9 +/- 0.3 cm2. The perioperative mortality was 3% in closed procedures and 3.4% in open procedures. Surviving patients were evaluated by questionnaires or phone interviews, and 129 patients were examined by two-dimensional echocardiography with the purpose of analyzing long-term results. Follow-up was 95% complete (Grunkemeier-Starr method), with a median of 18 years in patients with closed commissurotomy and 6.6 years in patients with open commissurotomy. The actuarial survival at 21 years was 60.8% (70% confidence limits 55% to 66%) in patients having closed commissurotomies and 60.6% (70% confidence limits 49% to 71%) at 22 years in patients having open commissurotomies. The "effective palliation" rate, defined by clinical and echocardiographic criteria, was 47% at 15 years and 15% at 20 years. We conclude that mitral commissurotomy is the procedure of choice in pure mitral valve stenosis and should be applied early. When performed in patients aged less than 40 years, a 78% (70% confidence limits 72% to 84%) survival at 18 years and 67% "effective palliation" at 15 years were observed. The closed valvotomy results of our study support the present trend toward use of percutaneous balloon valvotomy.

Accelerated hematopoietic recovery and protective effect of the cyclooxygenase inhibitor indomethacin in bacterial infection of neutropenic mice

The effects of indomethacin administration on Pseudomonas aeruginosa infection were investigated in neutropenic mice. Cyclophosphamide-treated mice received the drug at 2.5 to 12 mg/kg according to different regimens, to be challenged with a lethal intraperitoneal inoculum of P. aeruginosa 5 days after myelosuppression. A single exposure of the neutropenic mice to 7 mg/kg indomethacin during the first 6 to 48 hr after myelosuppression was found to optimally restore the animals' antibacterial resistance, both in terms of survival of infected mice and clearance of the organisms from the peritoneal cavity. However, when administered 24 hr before challenge, the same drug dosage had no effect in enhancing survival. Cure was associated with accelerated hematopoietic recovery, as revealed by peripheral blood leukocyte counts, spleen weight and cellularity, cellular response to infection in the peritoneal cavity, and enumeration in vitro of bone marrow and splenic granulocyte-macrophage colony-forming cells. Following indomethacin administration, a rapid burst in the levels of colony-stimulating activity was detected in the bloodstream, and exposure of splenic macrophages or marrow cells to indomethacin in vitro was found to result in enhanced expression of transcripts specific for granulocyte-macrophage colony-stimulating factor. These data support the notion that the administration of cyclooxygenase inhibitors may be useful in promoting hematopoiesis and reducing the risk of opportunistic infections in myelosuppressed hosts.

[L-T4 malabsorption determined by intolerance to cow's milk proteins and celiac disease in a patient with congenital hypothyroidism. A clinical case]

An infant with congenital hypothyroidism (CH) is described who in the course of thyroxin replacement therapy developed cow's milk protein intolerance (CMPI) and subsequently coeliac disease (CD). The presence of these two pathologies interfered with the intestinal absorption of L-thyroxin (L-T4) and made the appropriate management of CH difficult. A male patient, formula fed from birth, was screened for CH at 5 days of age. CH was confirmed and L-T4 treatment (6.8 micrograms/kg/day per os) begun at 35 days of age. Seen after 3 weeks because of feeding problems and impaired growth and with a serum T4 concentration of 4.7 micrograms/dl and a TSH of 56 mU/ml, his replacement dose was increased to 12 micrograms/kg/day. One week later, the child was hospitalized because of vomiting, acidosis and shock. CMPI was diagnosed and the child began a diet with a hydrolyzed milk protein food. After 7 weeks the serum T4 improved to 11 micrograms/dl, the TSH decreased to 10 mU/ml, while maintaining the 12 micrograms/kg dose. After 2 months an oral challenge with cow's milk confirmed the diagnosis of CMPI with a concomitant decrease in serum T4 to 6.4 micrograms/dl, while TSH rose to 64 mU/ml. Weight and T4 levels normalised with CMPI diet. At 12 months of age the patient presented anorexia and impaired growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term echocardiographic evaluation of closed and open mitral valvulotomy

From 1968 to 1989, 280 patients with post-rheumatic pure mitral stenosis underwent surgical commissurotomy; 134 a closed and 146 an open technique. Follow-up exceeded 15 years in 56.7% of the patients. Echocardiographic analysis was performed in 120 patients and disclosed a larger mitral valve area in patients who underwent open valvulotomy (1.9 +/- 0.5 cm2 vs. 1.5 +/- 0.4 cm2 for the closed technique, P < 0.0002). On the other hand, considering the occurrence of post-surgical mitral regurgitation at a level greater than, or equal to moderate, open valvulotomy produced less favorable results (18.5% vs. 5% for the closed technique, P < 0.01).

Experimental studies of immunotoxicity of a photosensitizing agent (Photofrin II) in mice

Immunotoxicity studies have been performed on the photosensitizing agent Photofrin II (PHFR), a porphyrin derivative used in photodynamic therapy. Hybrid CD2F1 (H-2d/H-2d) or inbred C57Bl/6 (H-2b) male mice were injected with graded doses of the agent (from 1.2 to 12 mg/Kg ip) on day -5, -3 and -1 before assays. The animals, or spleen cells collected from them on day 0 with respect to PHFR treatment, were tested for: a) competence of producing GVHD upon cell transfer into allogeneic, immunosuppressed recipients; b) graft response against challenge with allogeneic lymphoma cells; c) delayed-type hypersensitivity (DTH) against sheep red blood cells; d) in vitro response to mitogens; e) NK cell activity; f) in vitro generation of alloreactive cytotoxic T lymphocytes (CTL); g) resistance against the challenge of a sublethal dose of Pseudomonas aeruginosa. Moreover the LD50 of the drug given ip has been determined in male CD2F1 mice. The results show that PHFR, even at the highest doses used, does not affect most of the immunological parameters studied, except for a marginal inhibition of CTL generation and increment in proliferative responses to Con A or LPS. These data along with parallel studies performed by our group on human models in vitro, showing increased susceptibility of PHFR-treated tumors to NK or LAK effector cells, point out that PHFR, in the absence of systemic photoactivation, is essentially non-immunotoxic in vivo and could render tumor cells more susceptible to natural immunity.

Modulation of colony-stimulating activity by interleukin 1 in mice: opposing effects of combined treatment with indomethacin or prostaglandin E2

Following previous observations that interleukin 1 (IL-1) may have both positive and negative effects on the levels of circulating colony-stimulating factors (CSF) in mice, we have investigated the impact of human rIL-1 beta administration on serum concentrations of colony-stimulating activity (CSA, as defined by biossay) and macrophage-specific colony-stimulating factor (CSF-1, measured by RIA). In addition, we have studied the effects of IL-1 administered in conjunction with indomethacin or prostaglandin (PG) E2. Besides confirming the finding that exogenous IL-1 leads to a rapid increase in CSF detection, we obtained evidence that IL-1 may also result in the production of cyclo-oxygenase pathway products that down-regulate the IL-1-induced burst in CSA and CSF-1 levels. While co-treatment of mice with indomethacin led to a further increase in CSF detection, the combined exposure to IL-1 and PGE2 resulted in a significant impairment of the stimulatory activity of IL-1.

Modulation of circulating colony-stimulating activity in mice: combined effects of IL-1 and bacterial or indomethacin treatment

We have investigated the effects of interleukin 1 (IL-1) administration on circulating levels of colony-stimulating activity (CSA) in intact or neutropenic mice. Intact or cyclophosphamide-treated mice received human rIL-1 beta according to different regimens, and their sera were assayed for CSA at 4, 24 or 48 h. The results indicated that (1) cyclophosphamide alone significantly increased the level of circulating CSA, (2) administration of IL-1 to intact or neutropenic mice resulted in a biphasic pattern of CSA response, an early burst at 4 h being followed at 24-48 h by a significant decrease. In nongranulocytopenic mice, the combined treatment with IL-1 and bacterial cells also resulted in a biphasic pattern of CSA response. However, when IL-1 was administered in concurrence with the cyclo-oxygenase inhibitor indomethacin, sustained CSA levels could be observed for a prolonged period of time. These data expand upon our previous observations on modulation of CSA by IL-1 in granulocytopenic mice, and further support the concept that IL-1 may have both positive and negative effects on the expression of circulating CSA.

Antibacterial resistance induced by recombinant interleukin 1 in myelosuppressed mice: effect of treatment schedule and correlation with colony-stimulating activity in the bloodstream

We have investigated the effects of interleukin 1 (IL-1) administration on the ability of neutropenic mice to resist Pseudomonas aeruginosa challenge in vivo. Cyclophosphamide-treated mice received human rIL-1 beta at 7.0, 0.7, or 00.7 micrograms/kg, according to different regimens, to be challenged with a lethal ip inoculum of pseudomonas cells 5 days after myelosuppression. The repeated exposure of the neutropenic mice to an overall cytokine dosage of 7.0 or 0.7 micrograms/kg during the 4 days after myelosuppression was found to optimally restore the animals' antibacterial resistance. However, when administered as a single injection 24 hr before challenge, the same dosages of IL-1 had lower or no effect in enhancing survival, primarily leading only to a reduction in the amount of antipseudomonal chemotherapy required for cure. The regimen of IL-1 administration conferring optimal protection also resulted in a decrease in the number of pseudomonas cells recovered from the peritoneal cavity of infected mice. This regimen accelerated hematopoietic recovery in cyclophosphamide-treated mice. Assay of serum colony-stimulating activity (CSA) revealed that (a) cyclophosphamide treatment alone significantly increased the level of circulating CSA, (b) administration of a single dose of IL-1 to neutropenic mice induced an early, further increase in serum CSA, followed by depression, (c) a biphasic pattern of CSA response was also evident in mice repeatedly treated with IL-1. These results suggest that regulation of hematopoiesis may have an important role in the induction of antibacterial resistance in myelosuppressed hosts repeatedly treated with low dosages of IL-1.

Evaluation of antibacterial activity in experimental meningo-encephalitis in mice

Mice infected intracerebrally (ic) or intraperitoneally (ip) with Pseudomonas aeruginosa were treated subcutaneously with graded doses of five antibiotics all of which displayed anti-pseudomonal activity in vitro. The analysis of MIC, ED50 in the ip infection model (ED50-ip) and that in the ic system (ED50-ic) for each agent showed: gentamicin, the most active agent in vitro, was also active in vivo, with an ED50-ic nearly six-fold higher than ED50-ip; ceftazidime, considerably active both in vitro and in vivo, showed comparable values of ED50 in the two systems; ceftriaxone, also active in vitro, showed limited activity in vivo, its two ED50 values being similar; aztreonam, moderately active both in vitro and in vivo, showed comparable activity in the two infection models; carbenicillin, the least active agent in vitro, gave poor results in vivo, with an ED50-ic 2.6-fold higher than ED50-ip.

Natural resistance of mice pretreated with 5-(3,3'-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) + cyclophosphamide (Cy) against virus-induced lymphoma cells

Virus-induced leukemia was inoculated into histocompatible or allogeneic hosts pretreated with 5-(3,3'-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) + Cyclophosphamide (Cy), which abrogate endogenous cell proliferation and T-dependent graft responses, but not selected "natural resistance" (NR) activities. Marked impairment of lymphoma cell growth occurred mainly in the spleen of allogeneic mice with respect to that of histocompatible controls. Tumor inhibition was still present when lymphoma challenge was performed on day + 3 after Cy administration. Parallel studies on "natural killer" (NK) activity in vitro or in vivo showed that complete abrogation of the NK function was detectable on day + 3 or + 6 after Cy treatment. It was concluded that in vivo inhibition of lymphoma growth in mice pretreated with DTIC + Cy could be a drug-resistant NR at least in part distinguishable from the NK function.

Antilymphoma graft responses in the mouse brain: a study of T-dependent functions

The ability of mouse brain to provide T-dependent antilymphoma graft responses was studied in a model in which graded numbers of tumor cells were implanted intracerebrally into recipient hosts. By using survival criteria, it was possible to demonstrate the occurrence of both primary and secondary responses against tumor-associated histocompatibility antigens in allogeneic models as well as tumor-associated transplantation antigens in histocompatible recipients. The patterns of this intracerebral graft resistance did not differ significantly from those of peripheral T-dependent immune reactivity. The findings are discussed with regard to the concept of the brain as an immunologically privileged site.

Differential graft resistance of C3H mice pretreated with antitumor drugs against BALB/c bone marrow or lymphoma cells

Sequential treatment of mice with 5-(3,3'-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC) and Cyclophosphamide (Cy) produced long-term inhibition of endogenous cells proliferation in the spleen and impairment of classical allograft response, similar to that obtainable with lethal total body irradiation. The growth of BALB/c bone marrow or of virus-induced LSTRA leukemia of BALB/c origin, was studied comparatively in drug-treated or irradiated histocompatible (BALB/c x DBA/2)F1 or allogeneic C3H/HeN hosts. No splenic resistance of Hh type against bone-marrow cells was detected in C3H recipients, either irradiated or drug-treated, confirming previous studies on the Hh susceptibility of C3H strain. In contrast, strong transplantation resistance was detected in the spleen, liver and lung of the same hosts, irradiated or drug-treated, and challenged with LSTRA cells. It follows that Hh-susceptible mice are competent for mounting a localized radioresistant and drug-resistant response, directed against a virus-induced lymphoma.

Radioresistant inhibition of lymphoma growth in congenitally athymic (nude) mice

Several murine tumors were used to determine whether the phenomenon of tumor inhibition in athymic "nude" mice reported previously could be extended to other tumor systems in nude as well as conventional mice. The results with the L5MF-22 tumor line were confirmed, and similar data were obtained with the K36 leukemia of AKR mice and the LAF-17 leukemia of B10.A origin. This phenomenon of tumor inhibition has been called, tentatively, radioresistant inhibition of tumor and may be explained by one of several possibilities. The immunological origin of such tumor inhibition is supported by various observations. The data on tumor cell proliferation in spleens and liver of lethally irradiated mice were similar to previous findings on hemopoietic histocompatibility-incompatible lymphomas. Additionally, the nude mice were stronger responders against lymphoma cells than were conventional hosts. Another explanation is that the tumor inhibition is due to natural cytotoxicity.